Method for measurement of moisture content in granular materials



March 7, 1944.

R. L s'rEvraNs METHOD FOR MEASUREMENT 0F MOISTURE CONTENT IN GRANULARMATERIALS Filed Oct. 24, 1940 5 Sheets-Sheet 1 March 7, 1944; R L,STEVENS 2,343,340

METHOD FOR MEASUREMENT OF MOISTURE CONTENT IN GRQNULAR MATERIALS File@24, 1940 5 SheeS-Sheet 2 March 7 i944. R. L, STEVENS 2,343,340 METHODFOR `MEAstJmsp/IEN'I OF MOISTURE CONTENT INGRANULAR MATERIALS Filed Oct.24, 1940 5 Sheets-Sheet 5 hay.

AJ Y .5 F913.

' Zzaerzfow aberi'j Sfar/ens. 225 224 222 225 l T March 7, 1944. R. 1STEVENS 2,343,340

METHOD FOR MEASUREMENT OF MOISTURE CONTENTVI'N GRNULAR MTERIALS i FiledOct. 24, 1940' I. 5 Sheets-Snheet 4 March 7, 1944.

R. 1 STEVENS METHOD FOR MEASUREMEMT OF MOISTURE CONTENT IN GRANKULARMATERIALS Filed Oct. 24, 1940 5 ySheets-Sheet 5 Patented Mar. 7, 1944rrap STATES PATENT trice METHOD FDR MEASUREMENT F MOIS- BANULAB TUBECNTENT IN G BIALS MATE- Bobert 1L. Stevens, `Santa. Monica, Calif.,assigner, by mesne assignments, to Moisture Register Company, LosAngeles County, Calif., a corporation ci California.

Application October 24, i940, Serial No. 362390 5 Claims. (El. F15-183).

This invention relates generally to apparatus and systems designed formeasurement of moisture content in granular, shredded, pulp or powderedmaterials, or in materials in thin sheet or Y board-like form.

Conventional procedures for determining moisture content'in a givenmaterial have been generally coniined in the past to laboratoryprocedures which involve either the determination of loss of weight byheating; or the determination oi the amount of water recoverable fromthe sample by distillation. These laboratory procedures are inherentlytime consuming because of the steps of Aaccurate weighing involved andthe time required for carrying out the necessary drying or distillationsteps.

Electrical instruments have been provided in the past for quickdetermination of moisture content. Such instruments have in some in-vpression. For manyn materials, the pressure which I may thus use mayrange between values 'of the order of from about 1,000 to 1,500 poundsper square inch. The preferred form oi instrument provided by the.present invention, and

v with which this step of measurement under high compressive pressuremay be carried out, employs a cup adapted to receive the sample ofmaterial, and an electrode disk forming the bottom oi the cup and havingelectrodes adapted to produce an electric neld that will penetrate thesample oi material. A plunger fits inside this cup, and hydraulic meansare provided for pressing the plunger against the material with greatforce. A hydraulic pump and check valve system are provided fordevelopment oi the necessary iluid pressure. and to guard againstdeveloping a pressure higher than that for which the instrument isdesigned, a relief valve comes into operation when a predeterminedhydraulic pressure is achieved. In this connection, I may in someinstances, with some materials, bring the sample to such a state ofcompression that no to granular size, or closeness of packing, and

second, in the case of a compressible material, the variations ineiective density of the material.

A general object of the invention is the provision of an electricalmethod and instrument for measuring the moisture content in granular,shredded, pulp or powdered materials, or the like, or in compressiblesheet materials, in which the eiects of voids, air space, granular size,or density, are eliminated.

I have discovered that many if not all materials of the type in questionexhibit gradualx change in the measurable electrical characteristics ofinterest as they are compressed, but that finally a region is reached inwhich further compression causes little or no further change in thoseelectrical characteristics. In accordance with the present invention,therefore, I compress the material to this region (beyond which furthercompression has no substantial further effects), and then take themoisture measurement reading with the material under such comfurthercompression would have any sensible effect on the reading to be taken.In other instances, or with other materials, I may bring the sample to astate of compression such that further compression will have littleeilect on readings, and I may limit the compression of the sample to apredetermined point by the setting `or adjustment of the relie! valve,lso that calibration as well as all subsequent readings may be taken atthis reference point. In still other situations, or with still othermaterials, however, it may not be feasible to bring the sample to thestate of compression at which readings are no longer substantiallyinfluenced by further changes in compression. In such instances, therelief valve enables the compression o! the materiel at which theinstrument was calibrated to be duplicated time after time, so thatconsistent a readings are obtainable.

One present illustrative embodiment of the inventlon will be describedin detail, reference being directed to the accompanying drawings, inwhich:

Fig. 1 is a longitudinal vertical section through the instrument, takenon accordance with section line l-i of Fig. 2;

Fig. 2 is a transverse section taken on broken line 2 2 o! Fig. 1;

Fig. 3 is a plan view o! the instrument;

Fig. 4 is a section taken on line 4-4 oi Fig. 1:

Fis. 5 is-a section taken on line l-l oi Fig. 4;

Fig. 6 is an enlarged detail oi a portion of Fig.

1, showing a switch operating cam in switch closing position;

Fig. '7 is a fragmentary detail, similar to a portion of Fig. 6, andpartially 'in section in accordance with line 1-1 of Fig. 4;

Fig. 8 is a detail section taken on line 8-8/of Fig. 7;

Fig. 9 is a detail section taken on line S-Sl of Fig. 8;

Fig. 10 is a detail section taken on of Fig. 9;

Fig. 11 is a, diagram of the valves shown in Figs. '7 to 10;

Fig. 12 is a detail of Fig. 1; and

Fig. 13 is an electrical diagram of one suitable electrical system.

In the drawings numeral I designates generally a suitable sheet metalinstrument case, having a, frontwall I6, a sloping wall I1 extendingfrom the upper edge of wall' I6 to a rectangular aperture I8 whichextends between side walls I9, a short vertical wall 20 rising from therearward side of aperture I8, a top wall 2l, a back 22 equipped with asuitable removable door 23, and bottom 24. Mounted in sloping wall I1 isthe milliammeter or other instrument 25 by which the moisture content isread.

The mechanism by which the sample or material is placed undercompression is in the nature l line Ill-I0 of a. hydraulic press,generally designated at 26,

and this hydraulic press is supported by a suitable horizontal platen21, which in turn is mounted on the walls of the case dening apertureI8,

lthe hydraulic press extending above and below platen 21 as shown. y

Secured t0 the bottom' of platen 21 is a hydraulic cylinder 30, hereshown as having lugs 3l secured to platen 21 as by screws 32. Sl'idablewithin cylinder 30 is a piston 34, which is equipped section taken online I2-I2 excess travel of plunger 50 after it clears the top of thecup ring is avoided by arranging for rotation of the cross head 48 andthe attached plunger, about one of the tie rods 41, for instance to theposition shown in full lines in Fig. 3.

This movement is made possible by providing one' end of cross head 48with a slot 56 (see Fig. 3), so that the cross head is capable of beingdisengaged from the corresponding tie rod. The other end of cross head48 is provided with a simple perforation 51 which passes the tie rod andpermits rotation of the cross head thereon. l n

Means are preferably provided for yieldingly latching cross head 48 inclosed or operative p0- sition. As a simple and preferred. means forthis purpose, I show (Fig. 2) 'a ring shaped latching element 6 0surrounding the tie rod below the detachable end of the upper cross headand provided with a tapering nose 6I adapted to seat in a conicalcountersink 62 formed on the underside of the cross head, latchingelement 68 being urged in an upward direction by means of a coil spring63 seating on the upper end of a collar 64 sety tightlyon the tie rod. Asimilar collar 64 set on the other tie rod supports the cros's head andcylinderl 5U when swung to one side, and when the cross head andcylinder are in the closed'or operative position of Fig. 2 the crosshead may 'be supported both by the last mentioned collar with anysuitable form of packing, for instance chevron-shaped packing rings 35held between packing retainer ring 36 and inverted cup-shaped member 31secured on the reduced upper end portion 34a of piston 34 by screws 38.Downward pressure is applied to piston 34 byinjecting oil or othersuitable pressure fluid into the head end of cylinder 30 via fluidpassageway 40 and tubing 4I (see Fig. 1). This pressure is transmittedto a bottom cross head 45, which is secured to the bottom of piston 34as by screws 46. A pair of tie rods 41 passing through perforations 41ain platen I1 (see Fig. 2) connect bottom cross head 45 to a top crosshead 48. Secured as by screw 49 to the underside of top cross head 48 isa plunger 50 which is adapted to be moved downwardly into a cup ring 5Iresting on the upper side of frame plate 21, plunger 50 fitting the boreof ring 5I with close sliding fit. Cup ring 5I has a free sliding fitover a disk-shaped hard plastic block 52, preferably composed ofpolystyrene or other suitable insulation, preferably having low highfrequency losses, which is received Within a circular recess 53 in thetop of plate 21 and is secured toplate 21 as by screws 54. The cup ring5I and the plastic block 52 at the bottom dei-lne the sides and bottomof a pressure chamber .into which the sample to be tested is placed, andas pressure fluid is injected into cylinder 30, forcing piston 34 andthe two cross heads in a down- In'the embodiment of the invention hereshown 64 and by the spring pressed locking ring 6U pressed upwardlybythe spring 63 seating on the other collar` 64. Spring pressed lockingring 68 is readily cammed downwardly to permit the cross head to bemoved to or from the position of Fig. 2.

In the construction as here illustrated, collars 64 are provided withdepending sleeves 65 surrounding tie rods 41 with clearance, andtelescopically received inside said sleeve 65 are sleeves 66 mounted onand extending upwardly from frame plate 21. Preferably, the members 41,65 and 66 are not in sliding engagement, and serve simply to excludedirt from the interior of the instrument casing.

The aforementioned plastic disk 52 carries electrodes between or abovewhich is created an electric field capable of penetrating the materialon test. Such electrode elements may be of various kinds. They may, forinstance, constitute the two plates of a condenser, which is connectedin a circuit designed to measure changes in dielectric constant withvariations in moisture 4content in the material within the cup ring.Circuits of this type are well known and will require no descriptionherein. Preferably, however, I employ for this purpose a pair ofelectrodes which are in the output circuit of a high frequencyoscillatorsystem, the latter being designed tomeasure the power absorbed from thehigh frequency electrostatic field created between the electrodes by themoisture in the material on test. The electrodes are preferably in theform of concentric rings 10 and 1I embedded in and flush with the uppersurface of disk 52, being preferably molded into the disk by well knownmolding methods. A preferred oscillator system is disclosed and claimedin Patent No. 2,231,035 to Robert L Stevens and James P. Dallas,entitled Power absorption metering system, issued February 11, 1941, andto which reference may be directed for a full understanding. For presentpurposes it will suffice to refer to the schematic diagram of Fig. `13,in which electrode rings 10 and 1I are indicated'as energized by theoutput of ahigh frequency oscillator G. This oscillator preferably hasthe characteristics disclosed and claimed in the aforementionedapplication, and is indicated as having circuit leads connected tomilliammeter 25. The oscillator `is also indicated as having cathode andanode battery circuits A and B, controlled by the contacts of a switchS. The high frequency oscillating current delivered to the coplanarelectrode rings produces an electrostatic ileld that arches upwardlybetween the rings to penetrate the material within the cup'ring. Themoisture within the material absorbs power from this iield, thusreacting on or affecting the iield in such a way as to cause a change ofelectrical state within the oscillator, which is read by themilliammeter t. l

Electrical connections are made to the l'rings l@ and ii for instance asindicated in Fig. 1, conductive pins such as i2 extending downwardlythrough the disk-from the electrode rings, and

Y havim connected thereto suitable conductors such as i3 which leadthrough suitable insulation sleeves to the oscillator unit G, not shownin Figs. l. to l2, but which will be understood to be v mounted in anysuitable way inside housing i5.

A pair of coil springs i5 are provided for the purpose of elevatingpiston 3 -and plunger 5u upon release of hydraulic pressure insidecylinder 3d. As here shown, these springs are connected between bracketarms 16 mounted on the bottom of lower cross head t5 and anchor pinsscrewthreaded into the bottom of frame plate 2l.

A hydraulic pump 8u is provided for the purpose of delivering hydraulicfluid under pressure tol hydraulic cylinder 3U. This pump includes avertically arranged cylindrical pump body 8|A (see Fig.v d) having abore S2 extending downwardly from its upper end, and having a reducedbore it exnding downwardly from bore t2. The pump body Si is secured atthe bottom, as by brazing, within a cup shaped supporting member ttlformed at the end of a bracket arm 35,

extending from a mounting casting` du secured to the adjacent side walll@ of case l5. The pump has a plunger et receivable with clearancewithin bore 33 and slidable through a packing gland screwthreaded withinbore 2 (see Fig. d), suitable packing being provided, for instance asindicated at 92. The upper end of plunger 9@ is set into and brazed tothe bottom of a transverse sleeve 93 surrounding a cross pin at. Thereduced end portions 95 of said pin Se are connected by means ofparallel links t@ to the reduced end portionsl al of a similar pin 9E,and pin te is surrounded by a hub 99 formed at the swinging end of acrank arm Iii@ keyed onto a M941. projecting from crank arm 0e at theproper stroke limits of the latter An oil inlet passageway or port 0(see Fig. 7) opens inside bore 83 of pump 8|l. It will be understoodthat as manual crank arm |04 is worked up and down, motion istransmitted through crank arm |00 and links 96 to effect correspondingreciprocation of pump plunger 90, alternately drawing pressure iluidinto and forcing it back out of the variable clearance space between theplunger Sil and bore 83.

Figs. 4 and 5 show a suitable tank |20 for the hydraulic uid detachablysecured in any suitable manner to a wall of the exterior case; forinstance, it may be secured to a ange |2l positioned along the edge ofthe opening for door 23 by means of screws |2fl which are exposed whendoor 23 is removed. The tank is provided at the top with a breather hole|25 and at the bottom with a connection |26 with tubing |21. The tank isalso furnished with a iilling opening |28, closed by a screw plug |29.

Tubing I 2 leads from the bottom of tank IZ to e, connection |30 with aiiuid passage |3| extending upwardly into the bottom of a valve block 32(see Fig. 9). Passage |3| leads through a valve seat |33 for the valveball |33a of an intake valve |34, the enlarged valve chamber |35 aboveseat |33 being closed by plug |36. An angular passageway |31 leads fromvalve cham-A ber |35 to a horizontal passageway |38 (Fig. l0),

' and the latter intersects a. horizontal passagerotatable shaft lilithat projects through the adjacent side wall la of the housing. Shaftlul is iournaled in a tubular boss |02 formed inv.tegrally with theaforementioned mounting member 85, and has mounted on its exterior end amanually operable crank arm it furnished -with -a suitable handle ldd. Aplate w surrounds tubular boss lut adjacent the exterior surface of thehousing side wall (see Fig. d) and screws such as itl pass through saidplate and through side walt it into mounting member t@ to secure theparts tightly in assembly. To guard against the possibility of screwsIl' being loosened, plate E06 is preferably furnished with a cylindricalprojecting portion its which is positioned closely adjacent the hubportion lua oi crank |06. Stop lugs |09 are preferably mounted on theside of the case, in position to be engaged by a rubber covered bumperelement way |39 (see also Fig. '7) which extends out through a boss lollset into the side wall of pump body 8|, passageway |39 communicatingwith the aforementioned passageway or port lill in the pump. Boss it@ ispreferably brazedA to the pump body, and the valve body or block |32 isthus supported directly on thebody of the pump.

' On the up stroke of the pump plunger, pressure iiuid is drawn fromtank |2 via line |27; and past valve ball |33a. into and throughpassageway |31, E38, |39 and H0 to the pump. When the pump plunger isthen forced down, the :duid so drawn within the pump is displaced andforced outwardly via port Hu and passageway |39. Valve ball |3311, seatsat this time, and the uid passes upwardly through a passageway |42 andpast a valve ball M3 that normally seats at |46 within a valve chamber|45 of a discharge check block |32. The bore Ml of this iltting lt isconnected withl the aforementioned pressure iiuid line-tl by means` of asuitable pressure tight coupling it. As clearly illustrated in Fig. 7,bore itl in tting |59 communicates with valve chamber |45, and providesa shoulder at lilla which serves as a seat for the upper end of springlita. The pressure fluid expelled from the pump on the down stroke isthus discharged pest check valve M to pressure line 4| leading to theupper end ofhydraulic cylinder 3u. By reciprocating crank arm l,pressure uid is taken from tank |29 into the pump and forced from thereinto cylinder 30, causing downward movement of piston 3ft and plunger 50against springs 15 as previously described. The design of the apparatusis such that very high hydraulic\pressures may be developed, forinstance. sumcien to provide for a range of compressive pressures exrted by plunger the upper side of 'block |32, and provided with alongitudinal bore |51 in which is slidably mounted a valve operating rod|58, the valve body being provided at the top with a bonnet |59containing packing it@ for the valve rod stem lei. Secured to the bottomof valve rod |55 is a valve ball |53,

,which is adapted to seat on valve seat |65 at the bottom of valvechamber |65. Valve ball- |63 is normally held tightly on seat its bymeans of a later described spring. Extending downwardly from valve seat|64, so as to be controlled by valve A ball |53, is a passageway lll,which communicates with a horizontal passageway Hi connected withchamber its of valve itt by angular passageway |112. Valve chamber |65is connected by means of angular passageway ile' and horizontalpassageway and intersecting horizontal passageways |15 and |`l6 with theaforementioned vertical passageway 'iti that is in direct communicationwith tank |26. When it is desired to release the pressure in hydrauliccylinder 3o, valve plunger |58 is lifted to the position of Fig. 7.

This permits [the pressure fluid in view' of Fig. 1l, from which it willbe seen that the pump draws iiuid from the tank via line |21 and valve|34, and discharges it to line 4| and hydraulic cylinder through valve|46. Upon reaching predetermined maximum pressure in the hydrauliccylinder, further pressure fluid delivered from the pump by-passes viaautomatic relief valve |80 back to the incoming pressure iluid line |27.To release the pressure built up in the hydraulic cylinder, manualrelease valve is opened, allowing pressure iiuid from the hydrauliccylinder to i'low back to line |21.

The operating'stem itl of manual release |55 is connected with anoperating lever 200, which 'is pivotally mounted at 2Q! on a post 202extending from mounting lit (Figs. 6 and 12). This lever 2li@ has anotch m3 engaging a cross pin 2do carried by a clevis 205 to whichvalve'stem iti is connected. Lever 200 includes an operating arm 261i,and a 'tension spring 2% connected between the upper end of arm 2M and astationits seat.

cylinder 3|] to flow via tubing di, valve chamber |65, passageways |12,Hi and il@ to valveychamber'y |65, and from there via passageways VM,and |16 to passageway |34 and so on via line |21 to the tank.

An automatic relief valve itil is provided and and provided witha bore|83 for a valve plungerv i3d. A valve ball |65 secured to the lower endacts to limit the pressure which can be built up of valve plunger'ld isadapted to seat on a seat it formed in the bottom of valve chamber |87.'

Valve plunger |848 has a reduced upwardly extending stem W, which isreciprocable in a bore |9| formed in a head |92 screwed into the upperend of valve body itl. A compression spring |93 acting between head |92and a washer |915 engaging the plunger let urges said plunger and t.

valve ball |85 into tight seating engagement with seat |86.' Valvechamber |87 is in communica` tion via angular passageway |96 with theaforelmentioned passageway |76 leading back to the tank. Theaforementioned passageway ill, which will be recalled as being in directcommunication with the high pressure fluid in the hydraulic cylinder,connects with a horizontal pas sageway |91 that leads via verticalpassageway |98 to automatic relief valve chamber |81 through valve seat|85. Compression spring |93 is of such strength, either by selection,orby selection of a washer ist of proper thickness, that valve ball |35will bev unseated and permit high pressure fluid to ilow from thedischarge side of pump valve it through passageways lat, |76 and |3| totubing `|27 communicating with the tank when a predetermined maximumhydraulic pressure is reached. When this predetermined hydraulicpressure is reached, no further increase of pressure is possible,further operation of the pump simply resulting in pressure fluid beingbypassed through the automatic relief valve.

The valve system will be readily understood irom inspection of thedeveloped diagrammatic ary bracket 2te constantly urges lever 200 torotate right-handedly, as viewed in Fig. 6, so as to move valve stem itlin a downward direc-y tion, and thus maintain valve ball |63 tightly onThe manual release valve must of course be held seated under greaterspring pressure than is exerted against the automatic relieiI valve, soas to assure that the latter will have a chance to operate.

Arm 20| of lever 20d carries a pin 2|0, which is adapted to b e engagedby a flat plate cam 2|| that is mounted on the squared end portion 2|2aof a rotatable, manually operable shaft 2|2. Shaft 2 i2 is journaled ina bushing 2 I3 extending through vmounting t6 and through exterior casewall |9, bushing 2|3 being preferably permanentsecured to member 86 asby brazing. A nut member 2|5 is screwed onto bushing 2|3 on the outsideof wall i9, and a manual operating arm 2I6 is tightly mounted on theexterior end of shaft 2|2. When it is desired to operate manual releasevalve |55, manual operating arm 2|E is lifted, bringing a rising portion2|? of cam plate 2H to bear against pin 2 it carried by lever arm 2M,and thus swinging said arm from the position of Fig. 6 to that of Fig.'7. The stem iti of valve |55 is thus elevated and valve ball |63unseated, so as to permit by-pass of pressure fluid from the hydrauliccylinder back to the tank. Beyond rising portion 2|?, the cam has alconcentric circular portion 2id, onto which the lpin 2||| finally rides,and this portion of the cam holds the arm 2Q? in the release position ofFig. 7 against return spring 208 while the springs 'i5 then lower end ofthe aforementioned bushing 2|3, as clear ly illustrated in Fig. 12, andcarries at the top a flat spring switch-operating arm 22 as wel] asspaced and insulated switch arms 222, 223, 22# and 225. One pair ofthese switch arms are in the lament battery circuit, while the otherpair are in the plate battery circuit, as indicated in Fig. 13.

`The lower hooked end portion 23|! of arm 22| is engageable by a.shoulder 232 of cam plate 2|| when the cam plate is rotated fromtheposition of Fig.- 1 to that of Fig. 6. Such engagement causes deflectionof arm 22|, and resulting closure of the pairs of contacts carried bythe pairs of switch arms 222, 223 and 224-, 225, as will be understood.As will appear, cam plate rotates right-handedly, as viewed in Figs. 1and 6, in thus closing the switch arms, and such movement results fromdownward movement of operating arm 2 I 6.

An arm 223 is rotatably mounted on a. hub 234 of cam .plate 2|! (seeFig. 12) and is engaged by a pin 235 projecting rearwardly from the camplate as the latter is being rotated to'switch closing position.Thereafter, further rotation of the cam plate in a right-handeddirection must be accompanied by corresponding movement of arm 236,against the restraining influence of a return spring 23S connectedbetween arm 232 and th aforementioned bracket 209. As shown in Figs. 4and 6, the bracket 209 may be mounted on the switch carrying bracket226. When arm 2|6 is released spring 236 returns it and cam plate 2|| Yto the neutral position of Fig. 1. Preferably, cam

plate 2li is provided with a stop pin 238, which engagesthe lowerend'239 of bracket arm 22u to stop further rotation of the cam when thecam has been moved either to the switch closing position of Fig. 6, orthe valve opening position of Fig. '1. Upward movement of arm 233 beyondthe position of Figs. 1 and 7 is prevented by the engagement of theupper edge of said arm against a shoulder 22|@ on switch operating arm22| (Fig. `(i), this provision being made to guard against the arm 233being moved under the inuence of spring 236against cam pin 235 and sotending to rotate the cam left-handedly to a po sition in which it wouldengage and possibly move pin 2@ carried by valve operating arm 2Ill'.

The operation of taking a moisture test of a granular, powdered,shredded or other similar material, is as follows: The sample ofmaterial is placed in cup ring 5| and the upper cross head 48 thenlatched in position with plunger Ell in position to enter the cup ring.Then, with operating arm 2i@ in the neutral position of Fig. 1, pump 89is operated by means of crank arm |08 to pump pressure fluid from tank|26 into the upper end of hydraulic cylinder 30. This causes hydraulicpiston 32 to descend and to draw plunger 5@ down into the cup ring,compressing the sam- .ple of material between its lower end and theelectrode carrying block 52. 'Ihe pump is operated until fluid pressurewithin hydraulic cylinder 3|? reach` the predetermined value for whichautomatic relief valve |80 is adjusted. Further operation of the pumpsimply causes pressure to by-pass through the automatic relief valve, asabove described. A moisture reading is then taken by depressingoperating arm 2|6, which operation closes the contacts 0f switch S,thereby energizing the oscillator, and therefore the electrodes,whereupon meter 25 shows a delection. Following taking of the meterreading, operating arm 2m is elevated to rock cam plate 2H to theposition of Fig. 7, in which manual release valve |55 is held open. Thepressure uid 4 thereupon ows from hydraulic cylinder 30 back to tank$22, being expelled by the upward force exerted-on piston 3d by returnsprings l5. Elevation of operating arm 2|6 thus results in re- When themanual release valve is ilrst opened, there is a tendency for thepressure fluid to surge back into tank |20. To prevent this surgingpressure fluid from being ejected through vent |25 in the top of thetank, the connection |26 between the tank and pressure uid line |21 isplaced underneath a horizontal Vtank wall |2|la which is at an elevationsubstantially below 4 escape therethrough before the valve' ball againseats,- and the volume of this amount of oil may approximate, or atleast represent a large share of, the increment by which the volume ofthe material on test has been decreased by the pressure of the plunger.'I'he result is substantial fall of pressure and expansion of thematerial back to or toward its original volume. To guard against thiscondition, I preferably provide an air compression chamber incommunication with the high pressure oil system. As here shown, a.sleeve 25|).surrounds a. vertical portion of high pressure oil tubing6|, and has heads l25| and 252 connected to the tubing. A slot 253 isformed in the tubing in the lower portion .of thesleeve,

allowing oil'to enter the sleeve and to compress a volume of air in theupper end of the sleeve.

The trappedair, being highly compressed, expands as excess oilpasses'the relief valve, and thus tends to prevent sudden loss ofpressure in the high pressure system.

leasing the hydraulic pressure and in causing thehydraulic piston 3d andplunger 52 slowly torise.

Platen 2l is preferably provided with a gutter groove 255 surroundingelectrode block 52, and adapted to discharge at 4one side of the platenas at 255 (see Figs. l, 2 and 3). This gutter tends to catch anymaterial that may be spilled around the cup ring, especially duringremoval of the cup ring, and facilitates brushing such material from thetop of the platen. The groove is. also available to catch any oils orother liquids thatv may under any conditions be expressed from thematerial under compression.A

Thus far the description has been confined principally to granular andsimilar materials. The apparatus is suited also, however, to use withsuch materials as paper, cardboard, wallboard, fibre, padding, felt andthe like, which may be of the nature of fiat sheets or-strips, and whichare compressible to some degree. When it is desired to test suchmaterials a punch may be used to cut circular disks from the material,which disks have a diameter such as to t into the pressure cup so thatthe plunger may be mounted upon them and they may be held under pressurein the same manner as has been described above for granular materials.If the sheet stock from which the sample is cut is very thin, and,therefore, is 'of such dimensions that the sample thickness will not begreat enough to prevent the high frequency field of the electrodes frompenetrating through it, several such disks may be piled one upon anotherto give the required thickness. of any .desired shape, so long-as theycover the electrodes and can be passed between the tie rods of the unit,may be tested in the same man.- ner by removing the cup ring from theapparatus and placing the sheets directly upon the elec- Of course,sheets of materialv trades, after which the upper plunger may bellowered directly upon them.

`that substantially all expressible air has been removed, all voidspaces reduced as far as possible, and the material compressed in volumeuntil it becomes a. homogeneous mass of substantially maximum density.If the material is of such a nature that such a degree of compression isnot feasible, the compression is at least raised, if possible, to therange where further incre= ments of increased pressure have no more thanslight or negligible effects on the readings. Automatic limiting of themaximum compression by the automatic relief valve then assuresconsistent readings. I! materials are encountered which cannotpractically be compressed to the range described, i. e., where furthercompression would causebut slight further variations in readings, thenreliance for consistent results depends upon, rst, placing the materialunder a relatively high compression, so that variables are reduced asmuch as possible, and second, on the automatic relief valve to assurethat the material is placed under exactly the same compression for everytest.

The invention has been particularly described in the aspect of moisturemeasurement. How= ever, in situations where moisture is substantiallyconstant, or absent, or negligible as compared with the effects of someother substance asiaaeo influence on said iield while sustaining thecomto a predetermined point at which void spaces or ingredient that maybe present in variable or unknown quantities, and that may, like moisture, have an eiect on the iield of the electrodes that can be readwithin or at the oscillator, the instrument may be utilized to measureor indicate the presenceI and or qutity of such other substance oringredient.

I have now described in considerable detail one form of instrument bywhich my invention may be carried into practical eiect; it will beunderstood, however, that this is for illustrative purposes only, andthat various changes in design, structure and arrangement may be madewithout departing from the spirit and scope of the invention or oftheappended claims.

l. The method of making a moisture test of granular, powdered,shreddedor other loose or compressible materials, that comprisescompressing a sample of the material, creating a high frequency eld insaid material, and determining the moisture content of the material byits pression of the material at a pressure value suf-l ilcient thatfurther increases in pressure do not materially influence the result.

2. The method of making a moisture test of I granular, powdered,shredded or other loose compressible materials, that comprisescompressing a sample of the material substantially are eliminated andfree air expressed, creating a high frequency field in said material,and determining the moisture content of the material by its iniluence onsaid field while the compression of the material is sustained at saidpredetermined point.

` 3. The method of making a moisture testof granular,` powdered,shredded or other loose or compressible materials, that comprisescompressing a sample of the material against an electrode means adaptedto be energized to produce a iieldvwhich penetrates the material andwhich is affected by the moisture content in the material, increasingthe compression of the materialto a predetermined point beyond whichfurther increases have materially reduced eifects on the field, anddetermining the moisture content of the material by its influence onsaid ileld while the material is held at said compression point.

4. The method of making a moisture test -of granular, powdered, shreddedor other loose or compressible materials, that comprises compressing asample of the. material, creating a high frequency electric field insaid compressed material, whereby electric power is absorbed from saidfield by the material in an amount depending upon the moisture'contentof the ma- A terial, establishing the compression of the material at apredetermined point beyond which further increases in compression havemate-` rially reduced eiects .on vthe amount of power absorbed by thematerial, and determining the moisture content of the material from thevamount of electric power which it absorbs while said compression issustained.

5. The method of making a moisture test of granular, powdered, shreddedor other loose or compressible materials, that comprises com-A

